Toast the panko. Add the panko and avocado oil to a dry skillet over medium heat. Stir constantly for 3–5 minutes until evenly golden brown. Transfer immediately to a plate and spread out. Cool completely.
Once cool, stir the lemon zest and parmesan into the toasted panko. Do not add these while the crumbs are hot.
Prep the chicken. Pat dry with paper towels. Slice each breast horizontally into 2 thin cutlets. Pound between plastic wrap to an even 1/2-inch thickness. Season both sides with salt and pepper.
Breading station. Bowl one: flour, garlic powder, onion powder, salt, pepper. Bowl two: beaten eggs and water. Bowl three: the toasted panko mixture.
Dredge each cutlet in flour (shake off the excess), dip in egg (let it drip), then press firmly into the panko on both sides. Press — don't sprinkle.
Rest the breaded cutlets on a rack for 10 minutes.
Air fry. Preheat to 380°F. Spray the basket. Add the cutlets in a single layer without touching — work in batches if needed. Spray the tops. Air fry 5 minutes, flip, spray again, and cook 3–4 minutes more, until the internal temperature reaches 165°F.
Make the sauce. While the chicken cooks, melt the butter over medium heat. Add the garlic and cook 1 minute. Whisk in the flour and cook 1 minute. Slowly whisk in the cream and broth. Simmer 3–4 minutes until thickened.
Remove the sauce from the heat, then whisk in the lemon juice and Dijon. Season with salt and pepper.
Plate the chicken, spoon the sauce over the top, and serve immediately.